Otago University professor Andrew Geddis said the people stopped in the checkpoint could seek damages from police if they wanted to.
"Because the stops were unlawful, it means they were carried out in breach of the New Zealand Bill of Rights Act. Breaches of the New Zealand Bills of Rights Act can attract remedies. It is possible to get damages for those kind of breaches."
Geddis said the meeting attendees could approach police and ask if they were prepared to provide compensation for the unlawful stops.
"If the police were unwilling, it would be open to those people to take further court action," Geddis said.
"It's up to the people themselves, if the people are happy with the police's apology then that's quite alright."
Despite finding the stops to be an "illegitimate use of police power" the IPCA found the subsequent police welfare support visits did not breach the Privacy Act and were in accordance with operational policy and the duty of police to protect life and safety.
Susan Austen, the head of the Wellington branch of the euthanasia group, said yesterday she was pleased with the findings.
"I think that people should be able to go to someone's home and have a totally lawful meeting and gathering and not have to have any fear that there may be repercussions," she said.
Austen was found not guilty last month of helping Treadwell commit suicide, though she was found guilty of importing the euthanasia drug.
- Additional reporting by Newstalk ZB